1. Field of the Invention
This invention relates generally to ventilators for supplying gas to facilitate and support human respiration and particularly to ventilators which employ a high frequency jet of gas for respiratory therapy. More specifically, the present invention is directed to enhancing ventilation at supraphysiologic rates and especially to maximizing the tidal volume of gas delivered to a patient during respiration therapy while simultaneously minimizing patient discomfort and the possibility of causing or aggravating trauma. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited to high frequency jet ventilation. The use of high frequency jet ventilation has proven to be quite beneficial in the treatment of certain respiratory conditions. In high frequency ventilation, rather than moving gas in bulk quantity into the gas exchanging areas of the lungs, ventilation is achieved by enhancing the mass transfer processes in the lungs through high frequency oscillation of the supplied gas. However, as the pulsation frequency of the gas delivered by a jet ventilator increases, supplying the necessary tidal volume of inhalation gas becomes more difficult and is limited by the response time of mechanisms employed for generating the gas pulses. In addition, the requirements of reliability, ease of maintenance and susceptibility to sterilization are important design considerations for a ventilator. Portability is a further desirable characteristic. Accordingly, the principal objectives of the present invention are to provide a new and improved ventilation technique and a multi-frequency jet ventilator which operates in accordance with this technique and is compact, relatively easy to maintain, capable of being easily sterilized and supplies a maximized tidal volume of ventilation gas flow over a wide range of frequencies and duty cycles.